1. Technical Field
The present invention relates to a virtual image display such as a head mount display attached to a head of an observer.
2. Related Art
A virtual image display (image display device) has been proposed which has an external appearance similar to that of spectacles and processes an image formed by a display element such as LCD (liquid crystal display) by using optical systems to produce a virtual image observed by an observer (for example, see JP-A-2006-162767).
A virtual image display disclosed in JP-A-2006-162767 includes an image display unit having a display element (such as LCD), a projection lens (objective lens) and others and fixed to a temple of a spectacle frame, and a light guide member (base) fixed to a front of the spectacle frame.
The light guide member has an introduction mirror and a combiner at one end and the other end, respectively, of the light guide member.
The introduction mirror receives image light emitted from the display element and projected through the projection lens as collimated light, and reflects the image light such that the image light can be guided toward the combiner by total reflection on the introduction mirror within the light guide member.
The combiner reflects the image light received by the total reflection within the light guide member such that the image light can reach a predetermined position outside the light guide member (left or right eye of the observer).
Generally, the virtual image display of the type disclosed in JP-A-2006-162767 is used by a variety of observers having different head sizes. Therefore, the virtual image display needs to have sufficient flexibility in its structure for allowing use by various observers.
According to the virtual image display proposed in JP-A-2006-162767, however, the pair of the temples are fastened to the front of the spectacle frame, leaving a fixed space between the temples. In this case, the virtual image display is difficult to be used by various types of observers having different head sizes, which lowers the degree of convenience in use of the virtual image display.
There is an idea of a structure of the virtual image display which is equipped with a hinge mechanism or the like capable of rotating the temples with respect to the front of the spectacle frame so as to allow use of the virtual image display by various observers, for example.
According to the virtual image display disclosed in JP-A-2006-162767, the image display unit is fixed to the temple. Therefore, when the structure of this idea is applied, the image display unit rotates together with the temple. In this case, the positional relationship between the projection lens (optical axis) and the light guide member (light guide mirror) fixed to the front of the spectacle frame changes, which makes it difficult to introduce the image light toward the left eye or the right eye of the observer in a preferable condition (to allow observation of the image by the observer in a preferable condition).